Various types of flow-meters known in the art, such as thermal or Coriolis flow meters, may provide a mass flow rate measurement (e.g., kilogram/second) of a fluid. Other flow meters may include vortex-based sensing where, for example, the frequency at which the vortices are formed (shed) is essentially proportional to the volumetric flow rate of the fluid.
Mass flow meters typically generate mass flow rate of a fluid, and do not provide a direct volumetric flow rate measurement, and therefore volumetric flow rate may be derived by dividing the mass flow rate by density of the fluid. Consequently, such mass flow-meters, when used for volumetric flow rate measurements, may be adversely affected when a condition of the fluid is uncertain or changes in the field. The condition of the fluid, for example may include unknown gas density fluctuations, temperature fluctuations, gas mixture composition change, etc. On the other hand, vortex-based flow meters may provide a direct volumetric flow rate measurement which is insensitive or less sensitive to certain conditions of the fluid, such as density or composition changes. However vortex based flow meters are often bounded by a lower flow rate measurement limit, below which the fluid velocity is too low or inadequate to form vortices, making vortex based flow rate measurement infeasible.
As described above, a fluid may be characterized by a condition that represents a combination of one or more properties of the fluid. For example, the properties may include a composition of a fluid, a density of the fluid, a temperature of the fluid, a pressure of the fluid, or combinations thereof. For example, when the fluid is natural gas, the natural gas may have different compositions, such as, different proportions of methane, ethane, propane, butane, etc. Typically mass flow meters, known in the art, are factory calibrated based on determined conditions, such as composition, density, temperature, and pressure, of fluid. For example, flow meters (such as the mass flow meters) known in the art are factory calibrated for a determined composition or density of natural gas at standard temperature and pressure.
However, during field measurements, the conditions of the fluid may vary resulting in inaccurate flow rate measurements by flow meters, such as, the mass flow meters. Accordingly, it is desirable to provide cost-effective flow meters that may provide accurate and reliable flow measurements across a wide dynamic range of operation while being substantially impervious to fluctuations and unknown condition variations such as noted above.